The field of this invention is general surgery, thoracic surgery, trauma and critical care.
Chest drainage tubes are used following thoracic surgery, chest trauma or to treat certain medical conditions. The purpose of a chest tube is to remove buildup of excessive body fluids, contaminants or air from the thoracic cavity. The presence of an opening into the chest or thorax, created with or without a cannula will cause pneumothorax (collapsed lung). Negative pressure in the chest cavity is created by the chest muscles and diaphragm in order to cause lung expansion and resulting inspiration of a breath. Therefore, a hole in the chest will equalize pressure and prevent critical lung function, i.e. lung insufflation. Any cannula placed into a patient""s chest cavity for drainage must be sealed to prevent pneumothorax from occurring.
Current chest drainage cannulae, also called chest tubes, drainage catheters or drainage cannulae, are flexible polymer tubes, placed into the chest cavity and extending outside the patient.
Chest drainage tubes are placed using a surgically invasive procedure. Generally, if a surgical incision into the chest has not been made, the chest tube is usually placed with the aid of an internal trocar that stiffens the chest tube and allows for easier chest wall penetration during placement. The procedure begins with a skin incision large enough to accommodate the diameter of the selected chest tube. Chest tubes are typically 8 mm to 10 mm diameter. The internal trocar, having a sharp point, is placed inside the chest tube. The pointed end of the trocar chest tube combination is pressed through the skin incision and plunged into the thoracic cavity through the muscle, fascia and fat layers of the patient, through the rib space and into the pleural cavity. The trocar is removed and the chest tube is clamped to prevent pneumothorax.
When drainage is required, the clamp is opened and fluid, air and contaminants are removed from the thoracic cavity. The fluid, air and contaminants typically are removed, forcefully, by use of external vacuum or pumping systems. The clamp is closed once drainage is completed to avoid reflux of fluid and air back into the chest cavity and possible generation of pneumothorax or influx of contaminants (i.e. infectious agents).
Placement of current chest drainage tubes is an invasive surgical procedure. With any invasive surgical procedure, there exists a risk of iatrogenic trauma to the patient. Significant training is required to safely perform these procedures and this training may not have been completed by emergency personnel who are the first line of treatment for many patients experiencing trauma.
Improved valving mechanisms would increase functionality of chest drainage tubes and overcome issues that occur with clamp application and removal. There are also fewer steps required of the medical practitioner in chest drainage when a tube with an internal valving mechanism is employed. There may also be a problem with a chest tube being pushed too far into the patient, resulting in kinking, compromised drainage and potential iatrogenic damage to internal organs.
This invention relates to a catheter, tube or cannula for draining fluid, air and contaminants from the chest and a method of placement.
The cannula of the present invention includes an internal, semi-automatic valving mechanism, which allows for fewer steps and minimizes the chance of leaving the chest tube open to atmosphere when drainage is completed. The cannula of the present invention also comprises an external movable fixation device to prevent inadvertently pushing the cannula too far into the patient. The minimally invasive placement method of the present invention is beneficial in not only the emergency setting but also in the hospital setting by reducing the chance of iatrogenic injury to the patient.
The cannula is a polymeric tube, preferably with a metal spiral winding to prevent kinking or collapse, which is fenestrated at or near the distal tip at a plurality of sites. The cannula includes an interior valve or seal, located inside the drainage lumen of the cannula, operably able to prevent reflux or efflux of fluid, air and contaminants to or from the chest. The cannula includes an intracorporeal fixation device, located internal to the patient, to prevent outward dislodgement of the chest tube from the chest. The cannula also includes an extracorporeal fixation device, located external to the patient to prevent inward movement of the chest tube.
In one embodiment, application of a vacuum at the proximal end of the cannula causes the internal valve to open thus allowing free flow of fluid, air and contaminants from the chest through the cannula and into the drainage system. The drainage system is typically a vacuum powered, water sealed suction device and collection reservoir. Removal of the vacuum causes exposure of the valve to atmospheric pressure and subsequent closure of the valve, thus reflux of fluid, air and contaminants into the chest is prevented.
Alternatively, the valve could be operated by application of positive pressure (above atmospheric) for closure of the valve and application of negative or zero pressure to open the valve. External feedback systems utilizing pressure sensors or other devices are used to ensure patient safety with the positive pressure valve closure embodiment.
In another embodiment, the internal valve is placed at the proximal end of the cannula. This valve is fabricated from a soft polymeric compound or foam with a central hole that is normally closed. Application of a mechanical force through the center of the valve, with a hollow obturator, for example, opens the valve and allows flow through the hollow obturator. Removal of the hollow obturator causes closure of the valve and prevention of reflux back into the thoracic cavity.
In yet another embodiment, the valve is a duckbill valve that passively prevents reflux back into the thoracic cavity while allowing drainage from the chest cavity under application of appropriate pressure drop across the valve. Such pressure drop can occur from an increase of intrapleural pressure caused by buildup of fluids or by application of a vacuum to the outlet side of the valve.
In all embodiments, the valve systems are, preferably, integral to the cannula and unable to be separated from the cannula when, for example, the patient rolls over and stresses the connection.
The drainage cannula of the present invention includes an intracorporeal fixation or retaining device that prevents the cannula from being removed inadvertently from the patient. This intracorporeal device is, for example, an elastomeric or inelastic (i.e. angioplasty-type) balloon affixed to the exterior surface of the cannula. The balloon is passed inside the chest cavity and is inflated with sterile liquids or air to prevent withdrawal through the hole or wound in the chest wall. Inflation typically occurs using a balloon inflation lumen in the cannula, inflation ports between the lumen and the balloon, and an inflation device external to the cannula.
Additionally, the drainage cannula of the present invention includes an extracorporeal fixation device that may comprise one or more clips that are affixed to the exterior of the cannula in a movable fashion. These clips are, preferably, located proximally to the internal fixation device or balloon. They may be moved against the chest wall and frictionally engaged to the cannula shaft to prevent the cannula from being forced too far into the patient. Such extracorporeal fixation devices could be retrofitted to existing chest tubes to improve the functionality of existing chest tubes.
The chest drainage tube of the current invention is placed in a minimally invasive procedure. Placement is accomplished by first performing a surgical skin nick and then placing a hypodermic needle into the pleural space of the patient at the site of the skin nick. A J-tip guidewire is placed through the hypodermic needle and the hypodermic needle is removed. A percutaneous access device or trocar is placed into the central lumen of the chest tube and over the guidewire and routed into the pleural space.
In a further embodiment, the cannula is steerable. This is accomplished by use of a malleable, bendable trocar that can be shaped prior to insertion into the patient. In another embodiment, steerability is obtainable by heat setting the cannula with a curved shape. Axially moving a rigid straight trocar into the bent portion of the cannula from the proximal end causes the curved shape to straighten out. This controllable bending is useful for negotiating tight turns in the patient. In another embodiment, steerability may be obtained using actuators on the surface or within the interior of the cannula to force bending of the cannula. These actuators are typically electrically powered. An actuator comprises electrical leads, a power source, a compressible substrate, and shape memory materials such as nitinol. Such actuators may be distributed along the length of the cannula. The actuators may be placed so as to oppose each other. Opposing actuators are activated one at a time and not simultaneously.
The combination of minimally invasive placement and reduced steps to operate the chest drainage tube will benefit patients and medical practitioners by reducing errors, minimizing trauma, increasing ease of use, and improving patient outcomes.